Molding-system valve having knockdown retainer

ABSTRACT

Disclosed is: (i) a molding-system valve, (ii) a molding system having a molding-system valve, and/or (iii) a method of a molding-system valve, amongst other things.

TECHNICAL FIELD

The present invention generally relates to, but is not limited to,molding systems, and more specifically the present invention relates to,but is not limited to, (i) a molding-system valve, (ii) a molding systemhaving a molding-system valve, and/or (iii) a method of a molding-systemvalve, amongst other things.

BACKGROUND

U.S. Pat. No. 5,258,158 (Inventor: Dray; Published: 1993 Nov. 2)discloses a valve for an injection-molding screw, and the valve includesa differential piston, which closes a material flow path prior toinjection of a molding material.

U.S. Pat. No. 5,044,926 (Inventor: Dinerman et al; Published: 1991 Sep.3) discloses a valve for an injection-molding machine. The valve has arod for rotation and axial translation relative to an injection screw,with a retaining sleeve that limits axial movement of the rod.

U.S. Pat. No. 4,512,733 (Inventor: Eichlseder et al; Published: 1985Apr. 23) discloses a valve for an extruder, with movement readilychanged by a retracting-screw withdrawing pin and a replacing meteringunit.

U.S. Pat. No. 4,062,479 (Inventor: Szabo; Published: 1977 Dec. 13)discloses a valve for a reciprocating screw-injection machine, thevalves has a valve seat with an annular closure for effectingprotuberance.

SUMMARY

It appears that known molding-system valves may be difficult to service(clean and/or replace).

In a first aspect of the present invention, there is provided amolding-system valve, including a knockdown retainer.

In a second aspect of the present invention, there is provided a moldingsystem, having a molding-system valve that includes a knockdownretainer.

In a third aspect of the present invention, there is provided a methodof a molding-system valve.

In a fourth aspect of the present invention, there is provided amolding-system device, including a valve-removal cap connectable to abarrel of a molding system, the valve-removal cap configured for removaland installation of a knockdown retainer of a molding-system valve.

A technical effect, amongst others, of the aspects of the presentinvention is a reduction in time associated with servicing of amolding-system valve so that a molding system may be brought back intooperational mode quicker in comparison to using the known molding-systemvalves.

BRIEF DESCRIPTION OF THE DRAWINGS

A better understanding of the exemplary embodiments of the presentinvention (including alternatives and/or variations thereof) may beobtained with reference to the detailed description of the exemplaryembodiments along with the following drawings, in which:

FIGS. 1A, 1B, 1C and 1D are views of a molding-system valve according toa first embodiment (which is the preferred embodiment);

FIG. 2 is a longitudinal cross-sectional view of a molding-system valveaccording to a second embodiment;

FIG. 3 is a longitudinal cross-sectional view of a molding-system valveaccording to a third embodiment;

FIG. 4 depicts frontal views of variants of the molding-system valve ofFIG. 1; and

FIGS. 5A to 5C are longitudinal cross-sectional views of themolding-system valve of FIG. 1, according to a fourth exemplaryembodiment, used in a barrel of a metal-molding system.

The drawings are not necessarily to scale and are sometimes illustratedby phantom lines, diagrammatic representations and fragmentary views. Incertain instances, details that are not necessary for an understandingof the embodiments or that render other details difficult to perceivemay have been omitted.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

FIGS. 1A, 1B, 1C and ID are views of a molding-system valve 100(hereafter referred to as “the valve 100”) according to the firstembodiment. The valve 100 includes a knockdown retainer 110 (hereafterreferred to as “the retainer 110”). The retainer 110 is easily: (i)assembled (knocked up) to the valve 100, and/or (ii) disassembled(knocked down, dismantled) from the valve 100. The valve 100 is used ina molding system 10 examples of which are: (i) the HyPET™ System; (ii)the Quadloc™ System; (iii) the Hylectric™ System; and (iv) the MagnesiumMolding System, which are all manufactured by Husky Injection MoldingSystems Limited (Location: Bolton, Ontario, Canada; WWW-URL:www.husky.ca).

Preferably, the retainer 110 includes knockdown pieces 110A, 110B that:(i) interleave (dovetail, connect) with each other, and/or (ii)interleave (dovetail, connect) with a stem 106. the stem 106 includes orhas a stem tip 106A that extends axially from the stem 106. The retainer110 is a “forward” retainer 110; if the retainer 110 is a forwardretainer, the retainer 110 defines (preferably), at least in part, amelt passage 122. The retainer 110 appears flush mounted in FIG. 1A.

According to a variant, the retainer 110 includes a unitary body thatinterleaves (dovetails, connects) with the stem 106.

During a recovery cycle of the molding system 10, the valve 100 permitsan injection screw 102 (hereafter referred to as “the screw 102”) tomove a molding material through the valve 100 into an accumulation zone,which is positioned ahead of the valve 100. During an injection cycle ofthe molding system 10, the valve 100 prevents backflow of the moldingmaterial toward the screw 102 while the molding material is injectedfrom the accumulation zone into a cavity of a mold via a nozzle (notdepicted) that is attached to a barrel 104. The barrel 104 is sized toreceive the screw 102. Generically, the screw 102 is also called amolding-material processing structure.

Preferably, a stem 106 extends from the screw 102. The stem 106 may alsobe called: a stem, a spigot, a peg, etc. The stem 106 may be: (i)integral to the screw 102 or (ii) attachable to the screw 102.Preferably, the stem 106 includes a threaded shaft 114 that mates with athreaded bore 116 of a distal end of the screw 102. The retainer 110 isknockdown joinable to the stem 106. Preferably, the retainer 110 and thestem 106 are joined by a knockdown joint 117. An example of a knockdownjoint 117 is depicted in FIG. 1C. Once the retainer 110 is joined to thestem 106, the retainer 110 does not move relative to the stem 106.

A rearward retainer 108 is located rearward offset from the retainer110, and the rearward retainer 108 extends from the stem 106. Therearward retainer 108 and the stem 106 may be: (i) integral, and/or (ii)separable from each other. The concept of the retainer 110 is applicableto the rearward retainer 108.

A check ring 112 (hereafter referred to as “the ring 112”) defines abore so that the stem 106 is receivable in the bore of the ring 112. Theretainer 110 and the rearward retainer 108 cooperate to (i) retain thering 112, and/or (ii) to permit limited stroking of the ring 112.

FIG. 1A shows the valve 100 in which the retainer 110 is depicted in astate prior to the injection cycle of the molding system 10 in which ashot of molding material has been accumulated in the accumulation zone.The ring 112 has been made to abut the retainer 110 so that there is:(i) no gap between the ring 112 and the retainer 110, and/or (ii) a gap109 between the ring 112 and the rearward retainer 108.

FIG. 1B shows the retainer 110 depicted in a state during the injectioncycle of the molding system 10, in which the screw 102 moves the moldingmaterial in the accumulation zone into the mold. The ring 112 has beenmade to abut the rearward retainer 108 so that there is: (i) a gap 111between the ring 112 and the retainer 110, and (ii) no gap between thering 112 and the rearward retainer 108.

FIG. 1C is an exploded view of the valve 100. Preferably, the knockdownretainer 110 includes knockdown pieces 110A, 110B. The knockdown pieces(also called “the pieces of the retainer”) 110A, 110B are held togetherby a non-positive attachment. Preferably, the pieces of the retainer110A, 110B are constrained to stay together when they are positionwithin the barrel 104. Preferably, the retainer pieces 110A, 110B arenot fixedly attached to each other (such as with a bolt). The retainer110 is easily separable into multiple pieces or multiple sections (thatis, retainer pieces 110A, 10B; that is, a plurality of retainer pieces).

Preferably, the knockdown joint 117 joins the retainer 110 with the stem106 so that the retainer 110 is knocked down or off from the stem 106.The knockdown joint 117 also permits slidably fitting or mating of theretainer 110 with the stem 106, but in a non-positive manner (that is,by not using bolts, etc, to firmly and positively bolt or attach theretainer 110 with the stem 106). The knockdown joint 117 includes aslide-type joint, which includes: (i) a tongue 118, and (ii) a groove120 that is slide matable (slip engagable) with the tongue 118. Thetongue 118 extends from at least one retainer piece 110A, 110B. The stem106 defines the groove 120 (preferably, the groove 120 is defined aroundan outer surface of the stem 106). The knockdown joint 117 assists inmaintaining the retainer 110 in a substantially constant axial positionrelative to the stem 106. When the retainer 110 is installed in thebarrel 104, the radial position of the retainer 110 is held constant bythe inner wall of the barrel 104.

When the valve 100 is installed in the barrel 104: (i) an outer diameterof the retainer 110 abuts (or is proximate to) an inner diameter of thebarrel 104, and (ii) the retainer 110 maintains its relative (axial)position with the stem 106 while the valve 100 operates.

FIG. 1D is a cross-sectional view of the valve 100 of FIG. 1A. Inoperation, the screw 102 is made to rotate and to force a moldingmaterial into the valve 100 and through the melt passage 122. Once apredetermined amount of molding material has entered the accumulationzone, the screw 102 stops rotating and the screw 102 is thrust forwardlyto force the valve 100 to close (the ring 112 is made to abut therearward retainer 108) and thus the molding material is pushed out fromthe accumulation zone, through a nozzle (not depicted) and into a moldcavity (not depicted). During injection the ring 112 abuts the rearwardretainer 108 to prevent backflow of molding material from the valve 100towards the screw 102. Following injection, the screw 102 is retractedso that: (i) the rearward retainer 108 slides away from the ring 112 and(ii) the ring 112 is made to abut the retainer 110, which then opens thevalve 100 and allows molding material to pass through the valve 100 andinto the accumulation zone 180.

According to a variant, a tongue extends from a selected one piece ofthe retainer 110, through a bore in the stem 106 and engages a groovedefined by another selected piece or section of the retainer 110.

To clean or replace the components of the valve 100, the barrel 104 isdisconnected from the nozzle (not depicted). The screw 102 is movedforwardly such that the valve 100 exits the barrel 104. Since theslide-type joint is a non-positive attachment, the retainer 110 isreadily removable from the stem 106. In instances where a significantamount of molding material maintains the retainer 110 attached to thestem 106, a rubber mallet may be used to strike and thereby disengagethe retainer 110 from the stem 106. Once the retainer 110 is removed,additional components of the valve 100 may be accessed, cleaned andreinstalled or replaced by equivalent components. Following replacementof components and reinstallation of the pieces of the retainer 110(which may also be called a “multi-part forward end”), the screw 102 isretracted into the barrel 104, the barrel 104 is closed and preparationfor a subsequent cycle of the molding system 10 may begin.

Certain molten metals and metallic alloys (such as magnesium) used inthixomolding and/or metal molding react with oxygen at a temperatureabove the solidius temperature. As a result, a more involved process isrequired for replacement of valve components in a thixomolding system ora metal molding system since direct exposure of the metal alloy to airmay cause the metal to burn. Replacement of valve components in athixomolding or metal molding application is further discussed in thedescriptions of FIGS. 5A to 5C.

FIG. 2 is a longitudinal cross-sectional view of a valve 200(hereinafter referred to as “the valve 200”) according to the secondembodiment. To facilitate an understanding of the second exemplaryembodiment, the elements of the second exemplary embodiment (that aresimilar to those of the first exemplary embodiment) are identified byreference numerals that use a two-hundred designation rather than aone-hundred designation (as used in the first exemplary embodiment). Forexample, the retainer 210 of the second exemplary embodiment is labeled210 rather than being labeled 110.

A slide-type joint 217 slidably mates the retainer 210 with a stem 206.The slide-type joint 217 includes a tongue 218 and groove 220. Thegroove 220 is defined by the retainer 210. The tongue 218 extends fromthe stem 206, and the tongue 218 is matable with the groove 220 therebyassisting in maintaining the retainer 210 in a substantially constantaxial position relative to the stem 206 (once the retainer 210 isinserted into the barrel 204 as the tongue 218 and the groove 220maintain inter-engagement with each other). The outer diameter of theretainer 210 abuts the inner diameter of the barrel 204 to maintain thepieces or the sections of the retainer 210 in cooperation with eachother. Preferably, the outer diameter of the tongue 218 is less than theinner diameter of the ring 212. This arrangement improves ease ofassembly of the valve 200.

According to a variation not depicted), the knockdown joint 117, 217includes multiple tongues and grooves so that: (i) some tongues extendfrom the retainer 110, 210 while other tongues extend from the stem 106,206, and (ii) some grooves are defined by the retainer 110, 210 whileother grooves are defined by the stem. 106, 206.

FIG. 3 is a longitudinal cross-sectional view of a valve 300(hereinafter referred to as “the valve 300”) according to the thirdembodiment. To facilitate an understanding of the third exemplaryembodiment, elements of the third exemplary embodiment (that are similarto those of the first exemplary embodiment) are identified by referencenumerals that use a three-hundred designation rather than a one-hundreddesignation (as used in the first exemplary embodiment). For example,the retainer 310 of the third exemplary embodiment is labeled 310 ratherthan being labeled 110.

The slide-type joint 317 (optionally) includes a tongue 318 and groove320. The groove 320 is defined around the outer surface of the stem 306.The width of the groove 320 is configured to accommodate the full widthof the retainer 310. The tongue 318 extends from the retainer 310.

A profile shape of the tongue 118, 218, 318 and of the groove 120, 220,320 may be any one of a sharp-edged rectangular profile, a round-edgedrectangular profile, a semi-circular profile, and a wedge-like profile.

Preferably, the knockdown joint 317 includes a dowel 350. The dowel 350is used to engage (in a knockdown approach): (i) engage the retainer 310to the stem 306, and/or (ii) engage the retainer 310 to the stem 306.The following are variants of the dowel 350: (i) the retainer 310defines a retainer bore 352, the stem 306 defines a stem bore 354, and adowel 350 extends into the retainer bore 352 and into the stem bore 354,(ii) the retainer 310 defines the retainer bore 352, and a stem dowel(not depicted) extends from the stem 306 into the retainer bore 352,and/or (iii) the stem 306 defines the stem bore 354, and a retainerdowel (not depicted, but it is a modified dowel 350) extends from theretainer 310 into the stem bore 354.

According to a variant, the knockdown retainer 310 includes a unitarybody (structure) that is joined to the stem 306 by a dowel 350.

FIG. 4 depicts frontal views of variants of the valve 100 of FIG. 1. Thevariant retainers 110C, 110D, 110E, 110F, 110G, 110H include (but othervariants are not limited to) a 2-piece construction, a 3-piececonstruction or a 4-piece construction. The retainers 110C, 110D includeretainer pieces (two and three respectively) that are substantiallyequal in size. The retainer 110E includes retainer pieces (four pieces)that are unequal in size. The variant retainers 110C, 110D, 110E depictthe melt passage 122, 222, 322 defined as being circular in shape. Thevariant retainers 110F, 110G depict the melt passage 122 defined asbeing arcuate shaped. The variant retainer 110G depicts the melt passage122 defined as being defined in part by the barrel 104.

FIGS. 5A to 5C are longitudinal cross-sectional views of the valve 1200of FIG. 1 used in a barrel of a metal-molding system (preferable, athixo-molding system 1201). The valve 1200 is according to the fourthexemplary embodiment. To facilitate an understanding of the fourthexemplary embodiment, elements of the fourth exemplary embodiment (thatare similar to those of the first exemplary embodiment) are identifiedby reference numerals that use a twelve-hundred designation rather thana one-hundred designation (as used in the first exemplary embodiment).For example, the retainer 1210 of the fourth exemplary embodiment islabeled 1210 rather than being labeled 110. As previously mentioned,FIGS. 5A to 5C depict a method of replacing valve components of a valve100 that is operatively connected to a molding system 10, particularlyof a thixo-molding system.

FIG. 5A is a longitudinal cross-sectional view of a distal end of abarrel 1204 of the thixo-molding system 1201. A heater 1214 is coupledto the barrel 1204. A barrel head 1228 (also called a “cover”) isattached to the barrel 1204 by a set of bolts 1226A, 1226B. The barrel1204 houses a screw 1202 for processing a molding material (such as ametallic molding material). The valve 100 is attached to the distal endof the screw 1202. Any one of the valves 100, 200 or 300 may be attachedto the screw 1202.

To begin replacing components of the valve 100, the temperature of adistal end of the barrel 1204 is lowered by reducing or turning off theoutput of the heater 1214. As the metal molding material cools andsolidifies within the valve 100, the remainder of the material withinthe barrel 1204 is kept (maintained) in non-solid state by maintainingother heaters (not depicted) operational. The solidifying moldingmaterial proximate to the valve 100 is permitted to weld the valve 100to the barrel 1204, and in response a seal is created. The seal blocksoxygen from entering the barrel 1204 and reaching the molten moldingmaterial contained in the barrel 1204 once the barrel head 1228 isremoved from the barrel 1204. Since the seal created by the solidifiedmaterial is airtight, the bolts 1226A, 1226B can be loosened and thebarrel head 1228 may then be removed without incurring risk of exposingthe molten molding material (melt located behind the seal and in thebarrel) to air, whereupon it could ignite.

FIG. 5B is a longitudinal cross-sectional view of the distal end of thebarrel 1204 of a FIG. 5A following removal of the barrel head 1228.After the barrel head 1228 is removed from the barrel 1204, avalve-service cap 1220 (hereafter referred to as “the cap 1220”) isinstalled to the barrel 1204. The cap 1220 is: (i) attached to thedistal end of the barrel 1204 by a set of removal cap screws 1222A,1222B, and/or (ii) is preferably made of a weld-proof material (that is,the material does not become welded to the molding material) such as ahighly-thermally resistant plastic or rubber. The cap 1220 (also calleda cap) defines a catch basin 1224, and the cap 1220 is used to receivethe valve 100. Preferably, the cap 1220 is filled with an inert gas,such as argon, prior to installation of the cap 1220 onto the barrel1204. The inert gas does not react to molten metallic molding material(such as magnesium, etc). Alternatively, a port (not depicted) extendsfrom the cap 1220 so that the inert gas may enter the cap 1220 after thecap 1220 has been installed to the barrel 1204.

Once the cap 1220 is installed, the heater 1214 is made to supply heatto the distal end of the barrel 1204, increasing the temperature andreturning the solidified material located proximate to the valve 100 toa molten (non-solid) state. The inert gas does not react with the moltenmetallic alloy. When the solidified material within the valve 100returns to a molten state, the screw 1202 is translated forwardly,pushing the valve 100 into the catch basin. The heater 1214 is turnedoff so as to re-solidify the molten molding material located in thedistal end of the screw 1202 and the barrel 1204. The solidified meltcreates an airtight seal around the distal end of the screw 1202 and thebarrel 1204 to thus prevent air from entering into the barrel 1204. Theremoval cap screws 1222A, 1222B are then loosened and the cap 1220 isdetached or removed from the barrel 1204. At this point, the valve 100protrudes out of the distal end of the barrel 1204 allowing serviceaccess to components of the valve 100, such as the ring 112, which canbe inspected, removed, cleaned and/or replaced, etc. Since the retainer110 is non-positively engaged to the stem 106 (that is, it is knockablyremovable from the stem 106), the retainer 110 falls off of the stem106. At times, the retainer 110 may not simply fall off the stem 106since solidified molding material may still remain at the interfacesbetween the retainer 110 and the stem 106. In such situations, theretainer 110 can be disengaged from the valve 100 once the valve hasbeen made to protrude from the distal end of the barrel 1204 by strikingthe retainer 110 with a rubber mallet or similar device (once all themelt has solidified and the catch basin is removed).

FIG. 5C is a longitudinal cross-sectional view of the distal end of thebarrel 1204 of a FIG. 5A following replacement of the components of thevalve 100. The ring 112 and the retainer 110 have been replaced by a newring 1226 and a new retainer 1310 respectively. In this manner, theentire valve 100 does not need to be removed from the screw 1202 (or thescrew from the barrel). The new retainer 1310 is held in place, by aclamp or other retention means (not depicted), as the cap 1220 is slidover the valve 100. Once the installation cap has been fit over aportion of the new retainer 1310, the clamp or other retention means canbe removed and the cap 1220 can be made to abut the distal end of thebarrel 1204 thereby encapsulating the valve 100. Installation cap screws1232A and 1232B attach the cap 1220 to the barrel 1204.

Following attachment of the cap 1220, (i) the cap is pumped with inertgas and (ii) output of the heater 1214 is increased to melt thesolidified melt located in the distal end of the barrel 1204. The screw1202 is retracted when the solidified melt has sufficiently melted,pulling the valve 100 within the barrel 1204. Once the valve 100 issufficiently within the barrel 1204, the output of the heater 1214 isonce again reduced in the distal end of the barrel 1204 to create a sealof solidified melt. The cap 1220 is then removed and replaced by thebarrel head 1228 of FIG. 5A. Once the barrel head 1228 is installed, theheater 1214 is used to melt the solidified melt within the barrel 1204,allowing normal operation of the thixomolding system to resume normaloperation.

The description of the exemplary embodiments provides examples of thepresent invention, and these examples do not limit the scope of thepresent invention. It is understood that the scope of the presentinvention is limited by the claims. The concepts described above may beadapted for specific conditions and/or functions, and may be furtherextended to a variety of other applications that are within the scope ofthe present invention. Having thus described the exemplary embodiments,it will be apparent that modifications and enhancements are possiblewithout departing from the concepts as described. Therefore, what is tobe protected by way of letters patent are limited only by the scope ofthe following claims.

1. A molding-system valve for use with a screw being received in abarrel of a molding system, the molding system being configured toprocess a molten molding material, the molding-system valve comprising:a stem being configured to extend from the screw, the stem having a stemtip; a check ring defining a bore, the bore receiving the stem; aretainer extending from the stem, the retainer being offset from thestem tip of the stem; and a knockdown retainer being located proximatethe stem tip of the stem, the knockdown retainer being located offsetfrom the retainer, the knockdown retainer and the retainer cooperatingto permit limited stroking of the check ring between the knockdownretainer and the retainer, the knockdown retainer defining a meltpassage extending through the knockdown retainer, the knockdown retainerincluding: knockdown pieces being: (i) interleaved with each other, and(ii) interleaved with the stem, and after translating the screw so thatthe molding-system valve becomes pushed out from the barrel so that thestem, the check ring, the retainer and the knockdown retainer becomeexposed, the knockdown pieces being knocked down by striking theknockdown pieces so that the knockdown pieces become disengaged fromeach other, from the stem, and from the check ring.
 2. Themolding-system valve of claim 1, wherein: the knockdown pieces areknockdown joinable with each other.
 3. The molding-system valve of claim1, wherein: the knockdown retainer and the stem are joinable by aknockdown joint.
 4. The molding-system valve of claim 1, wherein: theknockdown retainer and the stem are joinable by a knockdown joint, theknockdown joint includes: a groove defined by the knockdown retainer;and a tongue extending from the stem, and the tongue being engagablewith the groove.
 5. The molding-system valve of claim 1, wherein: theknockdown retainer and the stem are joined by a knockdown joint, theknockdown joint includes: a groove defined by the stem; and a tongueextending from the knockdown retainer, and the tongue being engagablewith the groove.
 6. The molding-system valve of claim 1, wherein: theknockdown retainer and the stem are joined by a knockdown joint, theknockdown joint includes: a retainer bore being defined by the knockdownretainer; a stem bore being defined by the stem; and a dowel beingextendable into the retainer bore and the stem bore.
 7. Themolding-system valve of claim 1, wherein: the knockdown retainer and thestem are joined by a knockdown joint, the knockdown joint includes: aretainer bore defined by the knockdown retainer; and a stem dowelextending from the stem, and the stem dowel being extendable into theretainer bore.
 8. The molding-system valve of claim 1, wherein: theknockdown retainer and the stem are joined by a knockdown joint, theknockdown joint includes: a stem bore defined by the stem; and aretainer dowel extending from the knockdown retainer, and the retainerdowel being extendable into the stem bore.
 9. The molding-system valveof claim 1, wherein: the knockdown pieces are held together by anon-positive attachment.
 10. The molding-system valve of claim 1,wherein: the knockdown pieces are knockdown joinable to the stem. 11.The molding-system valve of claim 1,wherein: the knockdown pieces areconstrained to stay together when they are position within the barrel.12. The molding-system valve of claim 1, wherein: the knockdown piecesare held together by a non-positive attachment.
 13. The molding-systemvalve of claim 1, wherein: the knockdown pieces and the stem are joinedby a knockdown joint.
 14. The molding-system valve of claim 1, wherein:the knockdown pieces and the stem are joined by a knockdown joint, andthe knockdown joint includes: a slide-type joint, including: a tongue;and a groove being slide engagable with the tongue, the tongue extendingfrom at least one of the knockdown pieces, the stem defining the groove,and the slide-type joint maintaining the knockdown retainer in asubstantially constant axial position relative to the stem.
 15. Themolding-system valve of claim 1, further comprising: a slide-type jointslidably mating the knockdown retainer with the stem, the slide-typejoint including: a tongue; and a groove being defined by the knockdownretainer, the tongue extending from the stem, and the tongue beingmatable with the groove thereby assisting in maintaining the knockdownretainer in a substantially constant axial position relative to thestem, once the knockdown retainer is inserted into the barrel as thetongue and the groove maintain inter-engagement with each other, theouter diameter of the knockdown retainer abuts the inner diameter of thebarrel to maintain the knockdown pieces in cooperation with each other.16. The molding-system valve of claim 1, further comprising: aslide-type joint including: a tongue; and a groove being defined aroundan outer surface of the stem, a width of the groove being configured toaccommodate a full width of the knockdown retainer, the tongue extendsfrom the knockdown retainer; and a dowel being configured to: (i) engagethe knockdown retainer to the stem, and (ii) engage the knockdownretainer to the stem.
 17. The molding-system valve of claim 1, wherein:the molding system also includes a barrel head and a cap; the moltenmolding material is permitted to become solidified so that the moltenmolding material welds the molding-system valve to the barrel, and inresponse a seal is created, and the seal blocks oxygen from entering thebarrel and reaching the molten molding material contained in the barrel;a remainder of the molten molding material within the barrel ismaintained in non-solid state; the barrel head is removed from thebarrel once the seal is airtight so that the molten molding materialbehind the seal and in the barrel is not exposed to air; the cap isinstalled to the barrel; a distal end of the barrel is heated up, and inresponse solidified material located proximate to the molding-systemvalve is returned to a molten state; the screw is translated forwardlyso that the molding-system valve is pushed into the cap; solidificationof the molten molding material is permitted to seal off the barrel, andthe molten molding material becomes solidified so that the knockdownpieces become welded to each other; and the molding-system valve isserviced by: (i) removing the cap to expose the stem, the check ring,the retainer and the knockdown retainer, and (ii) knocking down theknockdown retainer by striking the knockdown pieces so that theknockdown pieces become disengaged from each other, from the stem, andfrom the check ring.